Polyamide elastomers are a resin compound that is widely used in various fields, such as packaging materials for food and the like; medical device members; members of electrical devices, machines, and precision instruments; and automobile members. The medical device members that are made of a polyamide elastomer include medical tubes and catheter balloons. For use in production of such medical device members, a polyamide elastomer is required to have moldability, such as extrusion moldability and blow moldability, which is the ability of the polyamide elastomer to be formed precisely into a desired shape, and dynamical properties, such as elasticity, elongation at break, and strength at break, which are the ability of the polyamide elastomer to withstand potential destruction caused by pressure or bending force applied during use.
Patent Literature 1 discloses a block polyether amide that is obtained by condensation polymerization of a certain polyamide having a carboxy group on either end, a polyoxyalkylene having an amino group on either end and having an alkylene group containing 3 or more carbon atoms, and a certain diamine. Patent Literature 2 discloses a polyether amide that is obtained by polycondensation of a polyamide-forming monomer, a polyoxyalkylene having an amino group on either end and having an alkylene group containing 3 or more carbon atoms, a certain diamine, and a certain amount of dicarboxylic acid. The polyether amides of Patent Literatures 1 and 2 are likely to have a certain degree of elasticity and impact resistance. However, in the polyether amides with the compositions described in Patent Literatures 1 and 2, use of the polyether having an alkylene group containing 3 or more carbon atoms is not enough to attain sufficient mechanical strength, such as elasticity, elongation at break, and strength at break. Therefore, further improvement has been demanded.
Patent Literature 3 discloses a polyamide elastomer that is obtained by polymerization of (A) a polyamide-forming monomer selected from certain aminocarboxylic acid compounds and certain lactam compounds, (B) at least one diamine compound selected from polyether diamines having a polytetramethylene oxide (PTMO) skeleton, branched diamines, branched alicyclic diamines, and norbornane diamines, and (C) a certain dicarboxylic acid compound. All of the diamine compounds used in the invention described in Patent Literature 3, however, have poor reactivity and thereby take a long time for polymerization. This may cause partial thermal cracking of the polymerization product during polymerization. This induces coloration of the resulting elastomer and causes insufficient progression of the reaction of the diamine compounds, impairing the strength characteristics of the resulting elastomer, such as elongation at break and strength at break.
Patent Literature 4 discloses a polyether-polyamide copolymer resin that has an elongation at break of 1000% or higher and a modulus of elasticity of 15 MPa or lower and is for use in coating of or impregnation into flexible fabric. This patent literature discloses a specific embodiment, which is a polyether polyamide resin obtainable by binding a soft segment and a hard segment together. The soft segment consists of a polyether polyamide that is composed of a polyether diamine compound having a C2-3 alkylene group and a certain dicarboxylic acid compound. The hard segment consists of a polyamide that is composed of a certain aminocarboxylic acid and/or a certain lactam compound. Here, the polyether component of the polyether polyamide resin described in Patent Literature 4 has poor reactivity, so that the resin strength at break is insufficient.